The 75-year-old archbishop was vacationing with his predecessor Cardinal William Levada in southern California and experienced some chest discomfort over the weekend.

On Aug. 28 the cardinal took the archbishop to Long Beach Memorial Hospital, where he was given an angiogram. His doctors recommended he stay overnight at the hospital. The next morning his cardiologists recommended surgery.

The archdiocese said it was “encouraged” by the initial report but added that the first 24 hours were “critical” to the archbishop’s recovery. The archdiocese asked for prayers on his behalf.

Archbishop José H. Gomez of Los Angles called for prayers in response to Archbishop Niederauer’s condition.

“My friends, please pray for our brother,” Archbishop Gomez said in a late evening announcement on his Facebook page Aug. 29.

“May our good God grant him peace in this time of trial and bring him to a speedy recovery. And may the Blessed Virgin Mary, our Mother, gain for him comfort and strength.”